Preheat the oven to 350 degrees F.
Crumble 8 cookies into small, bite-size pieces. Finely grind the remaining cookies in a food processor or blender. Add the butter and process until moist crumbs form. Press the mixture into bottom of a 9 1/2-inch spring form pan. Bake until golden, about 8 minutes. Remove from the oven and cool completely on a wire rack.
Spread all of the softened chocolate swirl ice cream over the crust. Sprinkle with half of the crumbled cookies and cover with 3/4 cup ganache (As necessary, microwave the ganache for 30 seconds to keep it at pouring consistency, but do not allow it to get too hot as it will melt the ice cream) and freeze until set.
Spread all of the softened mocha ice cream over the hardened ganache. Sprinkle with the remaining crumbled cookies. Freeze until very firm, at least 4 hours. Cut around pan sides to loosen cake. Turn the cake out onto a wire rack set over a baking sheet. Pour the ganache over the top and sides of the cake. Let sit and pour remaining ganache over so the cake is completely coated with chocolate.
Freeze on the wire rack until very firm, at least 4 hours. Serve cake straight from the freezer.
Yield: 8 to 10 servings